The present disclosure relates to thermoplastic polymer alloy compositions and processes for manufacture thereof.
Thermoplastic polymer alloy compositions have been developed to replace polyvinyl chloride for the fabrication of many articles. In the automotive field, thermoplastic polymer alloy compositions have been used for the fabrication of articles such as interior sheathing, including instrument panel skins, door panels, air bag covers, roof liners, and seat covers.
The current fabrication process includes the steps of melt blending and pelletizing a thermoplastic polymer alloy composition. The formed pellets are then fed into an extruder to form sheets of the pellets. The processing steps continue with embossing the sheets, applying a primer on a bottom surface of the sheet, heat curing, applying a primer on a top surface of the sheet, heat curing again, applying a top coat (e.g., paint) and heat curing again. After this multiple step process, the resultant sheets can be used to form articles of manufacture such as interior vehicle sheathing. The primer in the bottom surface of the sheet is typically needed to allow adhesion to the understructure, such as urethane foam understructures.
As mentioned, the surfaces of thermoplastic polymer alloy composition sheets are generally treated prior to applying paint or adhering to understructures. Various methods have been used to attempt to increase the surface activation of thermoplastic polymer alloy composition having substantial amounts of polypropylene and/or rubber. For example, primers or adhesion promoters such as chlorinated polyolefins have been used to improve the adherence of thermoplastic polymer alloy compositions. However, the chlorination process is highly corrosive, typically requiring glass lined reactors. Further, the reaction generally required relatively high residence times, thereby resulting in higher manufacturing cost for chlorinated thermoplastic polymer alloy compositions. In addition, at least two additional process steps are required to apply the liquid primer and hot air oven drying on both sides of the thermoplastic polymer alloy composition sheet.
There is a need in the art for a thermoplastic polymer alloy composition having improved adhesive properties in order to minimize or obviate the need for a separate surface primer activation step.
The drawbacks and disadvantages of the prior art are overcome by a thermoplastic polymer alloy composition and processes for preparing same, wherein the composition comprises a blend of about 20 to about 40 weight percent (hereinafter xe2x80x9cwt. %xe2x80x9d) polypropylene; about 20 to about 50 wt. % uncrosslinked ethylene copolymer; about 2 to about 15 wt. % functionalized polymers, which functionalized polymers include maleated polypropylene; and about 1 to about 10 wt. % amines, which amines include long chain amines.
The processes generally comprise mixing the foregoing compositions. In one embodiment, the process comprises melt blending the foregoing compositions. In another embodiment, the process comprises in-line compounding for direct sheet extrusion of the foregoing composition.